<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
    .navgater{
        width: 600px;
        margin: 10px auto;
    }
    .navBar {
        color: #000;
        background: #f1f1f1;
        box-shadow:  0 2px 4px 0 rgba(0, 0, 0, 0.16), 0 2px 10px 0 rgba(0, 0, 0, 0.12)!important;
    }
    .navBar::after{
        display: block;
        content: '';
        clear: both;
    }
    a {
        text-decoration: none;
        display: block;
        padding: 8px 16px;
        
    }
    .children {
        position: absolute;
        color: #000;
        background: #fff;
        display: none;
        top: 100%;
        left: 0;
        box-shadow: 0 2px 4px rgba(0, 0, 0, 0.16),
        0 2px 10px 0 rgba(0, 0, 0, 0.16)!important; 
    }
    .children::after {
        display: block;
        content: '';
        clear: both;
    }
    .more:hover  .children {
        display: block;
    }
    a:hover {
        background: #999;
    }
    a:active {
        color: #000;
    }
    a:link {
        color: #000;
    }
    a:focus {
        color: #000;
    }
    a:visited {
        color: #000;
    }
    .children a{
       min-width: 50px;
    }
    li {
        list-style: none;
        float: left;
        position: relative;
    }
    .items {
        width:600px;
        margin: 20px auto;
        color: white;
    }
    .item {
        margin-top: 30px;
        padding: 1px 16px;
        line-height: 1.5;
        border-radius: 3px;
    }
    .item p {
        margin: 1em 0;
    }
    h3 {
        font-size: 24px;
        margin:10px 0;
        font-weight: bold;
    }
    .item span {
        float: right;
        font-size: 24px;
        cursor: pointer;
        font-weight: bold;
        text-decoration: none;
    }
    .success {
    background-color: #4CAF50;
    }
    .info {
    background-color: #2196F3;
    }
    .danger {
    background-color: #f44336;
    }
    .warning {
    background-color: #ff9800;
    }

    </style>
</head>
<body>
    <div class="navgater">
        <ul class="navBar">
            <li><a href="#">首页</a></li>
            <li><a href="#">作品</a></li>
            <li class="more">
                <a href="#" >更多</a>
                <div class="children">
                    <a href="#">gitHub</a>
                    <a href="#">博客园</a>
                    <a href="#">知乎</a>
                </div>
            </li>
        </ul>
    </div>
    <div class="items">
         <div class="item success">
             <span>×</span>
             <h3>恭喜你</h3>
             <p>获得本周最佳员工，继续加油吧</p>
         </div>
         <div class="item info">
             <span>×</span>
             <h3>通知</h3>
             <p>今天晚上,加班</p>
         </div>
         <div class="item danger">
             <span>×</span>
             <h3>天啊</h3>
             <p>又出了好多Bug啊</p>
         </div>
         <div class="item warning">
             <span>×</span>
             <h3>警告</h3>
             <p>再不干完个项目，就完蛋了</p>
         </div>
    </div>
</body>
</html>